Michael Woolf,

You'll be happy to find that there's a "Piano Melodico G.Racca Club" in
Italy which maintains a museum that includes a large quantity of original
music.  The great thing is that they also offer copies of that music for
48-, 73-, and 75-note models, and some replacement parts!

See: http://www.pianomelodico.com/ 

The correct spelling, "Melodico" (rather than "Melodica"), will help find
information on the Internet.  The ending "-a" denotes a handheld mouth-
blown keyboard organ -- not exactly the same instrument.

Todd Augsburger
todd@rollerorgans.com.geentroep [drop .geentroep to use]
Roller Organs
http://www.rollerorgans.com